JPH0644674U - Electric steering angle imparting device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the outer diameter of the device to facilitate installation in narrow underfloor spaces. [Structure] The output shaft 17 is axially displaced to give a steering angle to the rear wheels. The male screw portion 29 formed on the output shaft 17 and the female screw 33 on the inner peripheral surface of the nut piece 32 are irreversibly engaged. When the steering angle is applied, the nut piece 32 is rotated by the electric motor. The nut piece 32 is rotatable only and does not move in the axial direction. The output shaft 17 only displaces in the axial direction and does not rotate.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The electric steering angle imparting device according to the present invention is incorporated into a four-wheel steering device for automobiles, and imparts a steering angle to the rear wheels in relation to the movement of the steering wheel or independently of the movement of the steering wheel. Use to do.

[0002]

[Prior art]

 To reduce the turning radius of the vehicle so that the course can be changed easily on a narrow road, or to maintain the stability of the vehicle even when changing the course at high speeds, use the steering wheel. In recent years, four-wheel steering systems that move not only the front wheels but also the rear wheels when operated have become popular.

4 to 5 show an example of such a four-wheel steering device described in Japanese Patent Application Laid-Open No. 61-146682. The detection signals of the steering angle sensor 2 and the vehicle speed sensor 3 that detect the operation amount and the operation speed of the steering wheel 1 are sent to the controller 4. Then, the controller 4 energizes the electric motor 5 based on the detection signals sent from both the sensors 2 and 3.

The rotation of the electric motor 5 is transmitted from the worm 7 fixed to the output shaft 6 to the worm wheel 8, the transmission shaft 9 having the worm wheel 8 fixed at one end thereof, and the other of the transmission shaft 9 The pinion 10 fixed to the end is rotated. Since the pinion 10 meshes with the rack 12 that is fixed to the intermediate portion of the output shaft 11, the output shaft 11 is eventually moved in the axial direction (left and right in FIG. 4) as the electric motor 5 is energized. Direction).

The axial displacement of the output shaft 11 is transmitted to the rear wheels 15, 15 via the tie rods 13, 13 and the knuckle arms 14, 14 and a steering angle is given to each of the rear wheels 15, 15. Since the worm 7 and the worm wheel 8 are irreversibly engaged with each other, the worm wheel 8 will not be affected even if a torque in the rotational direction is applied to the worm wheel 8 when the electric motor 5 is not energized. Does not rotate. Therefore, when the electric motor 5 is not energized, the rear wheels 15, 15 do not move due to a disturbance such as lateral G.

[0006]

[Problems to be solved by the device]

 The electric steering angle imparting device of the present invention is designed to be small in size, so that it can be installed in a narrow space and facilitates the design of a four-wheel steering device.

In the case of the conventional device shown in FIGS. 4 to 5, the transmission shaft 9 is provided in a twisted positional relationship with the output shaft 11, and the worm wheel 8 and the pinion 10 are provided at both ends of the transmission shaft 9, respectively. And the worm 7 meshed with the worm wheel 8 is fixed to the output shaft 6 of the electric motor 5. As a result, the installation position of the electric motor 5 is largely separated from the output shaft 11, and the outer diameter dimension of the electric steering angle imparting device becomes considerably large at the installation portion of the electric motor 5.

The electric steering angle imparting device for imparting a steering angle to the rear wheels has to be installed in a limited space under the floor of the automobile, and it is not preferable that the outer diameter dimension is increased as much as possible. The electric steering angle imparting device of the present invention has been devised in view of such circumstances.

[0009]

[Means for solving the problem]

 The electric steering angle imparting device of the present invention includes a housing and an output shaft that is supported inside the housing so as to freely displace only in the axial direction, and imparts a steering angle to the wheels in accordance with the displacement in the axial direction. A male screw portion fixedly provided on the outer peripheral surface of the intermediate portion of the output shaft; a nut piece rotatably supported inside the housing at a peripheral portion of the male screw portion; And an electric motor that drives the motor to rotate. The male screw portion and the female screw formed on the inner peripheral surface of the nut piece are irreversibly engaged so that torque can be transmitted only from the nut piece to the output shaft.

[0010]

[Operation] When the nut piece is rotated by the electric motor during operation of the electric steering angle imparting device of the present invention configured as described above, the female screw and the male screw formed on the inner peripheral surface of the nut piece The output shaft, to which the male screw portion is fixed, is displaced in the axial direction based on the screw engagement with the portion. A predetermined steering angle is given to the wheels based on the displacement of the output shaft.

Since the female screw and the male screw portion are irreversibly engaged with each other, the nut piece does not rotate even when a force is applied to the output shaft from the wheel side in the axial direction. . Therefore, even when an external force such as lateral G is applied to the wheel, the wheel is not displaced and the vehicle is prevented from wobbling.

[0012]

【Example】

 1 to 3 show an embodiment of the present invention. The tubular housing 16 with both ends open is fixed below the floor of the automobile with its axial direction (the left-right direction in FIG. 1) oriented in the width direction of the automobile. An output shaft 17 is inserted inside the housing 16. Tie rods 13, 13 and knuckle arms 14, 14 are provided between both ends of the output shaft 17 and the rear wheels 15, 15 (FIG. 4), as in the case of the conventional structure shown in FIG. Therefore, with the displacement of the output shaft 17 in the axial direction, a steering angle is given to the rear wheels 15, 15.

A rack 18 is formed at a portion of the output shaft 17 which is close to one end of the intermediate portion (close to the left in FIG. 1), and the rack 18 and the pinion 19 are meshed with each other. The pinion 19 is disposed inside the housing 16 in a twisted positional relationship with the output shaft 17, and is rotatably supported by a pair of rolling bearings 20 and 20, as shown in FIG. The output shaft 17 is prevented from rotating by the engagement of the rack 18 and the pinion 19.

A cylinder portion 21 that is orthogonal to the output shaft 17 is provided at a portion of the housing 16 opposite to the rack 18. Inside the cylinder portion 21, a pressing piece 22 made of a slippery material such as nylon and Delrin and a compression spring 23 are inserted in order from the inner side facing the outer peripheral surface of the output shaft 17. . A lid piece 24 is screwed and fixed to the open end of the cylinder portion 21. Therefore, the pressing piece 22 presses the output shaft 17 toward the pinion 19 by the elastic force of the compression spring 23. As a result, the backlash of the meshing portion between the rack 18 and the pinion 19 is eliminated (becomes zero).

An input shaft 27 of an encoder 26 is connected to an end of the pinion 19 via a joint 25. Therefore, this encoder 26 converts the displacement amount of the output shaft 17 in the axial direction into a rotation angle and detects it. The detection signal of the encoder 26 is input to a controller (not shown) for controlling the electric motor 28 described later.

On the other hand, a male screw portion 29 is formed integrally with the output shaft 17 on the outer peripheral surface of the output shaft 17 near the other end of the intermediate portion (to the right in FIG. 1). The male screw portion 29 is formed of a trapezoidal screw, a square screw, or the like having a sufficient strength and capable of transmitting a large torque.

A portion of the end portion of the housing 16 located around the male screw portion 29 has a large diameter portion 30. A substantially cylindrical lid 31 is screwed and fixed to the end opening of the large diameter portion 30. The nut piece 32 is rotatably supported in the space 44 surrounded by the large-diameter portion 30 and the lid 31. The lock nut 38 serves to prevent the lid 31 from loosening.

Then, the female screw 33 formed on the inner peripheral surface of the intermediate portion of the nut piece 32 and the male screw portion 29 are screwed together. The male screw portion 29 and the female screw 33 have a relatively fine pitch. Therefore, when the nut piece 32 rotates, the output shaft 17 is displaced in the axial direction. However, even if a force is applied to the output shaft 17 in the axial direction, the nut piece 32 does not rotate. Absent. That is, the male screw portion 29 and the female screw 33 are irreversibly engaged so that torque can be transmitted only from the nut piece 32 toward the output shaft 17.

A portion of the inner peripheral surface of the nut piece 32, which is separated from the female screw 33, has a larger diameter than the male screw portion 29 to prevent interference with the male screw portion 29. A collar-shaped worm wheel 34 is formed integrally with the nut piece 32 on the outer peripheral surface of the intermediate portion of the nut piece 32.

The deep groove type ball bearings 35, 35 for rotatably supporting the nut piece 32 are arranged such that the inner rings 36, 36 of the deep groove type ball bearings 35, 35 sandwich the worm wheel 34, respectively. It is fitted and fixed on the outer peripheral surface. The outer rings 37 and 37 of the ball bearings 35 and 35 are fitted and fixed to the inner peripheral surface of the large diameter portion 30 or the lid 31, respectively.

A worm 39 is rotatably supported by the housing 16 in the large-diameter portion 30 by a ball bearing 40 and a slide bearing 41. The worm 39 is arranged in a twisted positional relationship with the output shaft 17, and is screwed with the worm wheel 34. The engagement state between the worm 39 and the worm wheel 34 may be reversible or irreversible.

Further, one end (the right end in FIG. 2) of the worm 39 is connected to the output shaft of the electric motor 28 via a joint 42. Reference numeral 43 is an encoder for detecting the number of rotations of the electric motor 28.

When the output shaft of the electric motor 28 is rotated in order to impart a steering angle to the rear wheels by the electric steering angle imparting device of the present invention configured as described above, this rotation causes the joint 42 and the worm 39 to rotate. Is transmitted to the nut piece 32 via the worm wheel 34, and the nut piece 32 rotates.

When the nut piece 32 rotates in this way, based on the screwing of the female screw 33 formed on the inner peripheral surface of the nut piece 32 and the male screw portion 29 formed on the output shaft 17, The output shaft 17 is displaced in the axial direction. Then, based on the displacement of the output shaft 17, a predetermined steering angle is given to the rear wheels.

Since the female screw 33 of the nut piece 32 and the male screw portion 29 of the output shaft 17 are irreversibly engaged with each other as described above, the rear wheel side is connected to the output shaft 17 in the axial direction. Even if a large force is applied, this force is only supported by the ball bearings 35, 35, and the nut piece 32 does not rotate. Therefore, even when an external force such as lateral G is applied to the rear wheels, the rear wheels are not displaced and the vehicle can be prevented from wobbling.

In the illustrated embodiment, the central shaft of the nut piece 32 and the output shaft of the electric motor 28 are arranged in a twisted positional relationship, and the worm type speed reducer is provided between both shafts. Since the force required to rotate the piece 32 is not so large, it may be possible to arrange these two shafts in parallel and to provide a transmission mechanism by a toothed belt or a gear between the two shafts.

Further, by fixing the rotor to the nut piece 32 and arranging the stator around the rotor, a cylindrical electric motor is provided around the nut piece 32, and by the electric motor, The nut piece 32 can be directly driven to rotate. With this structure, the outer diameter of the electric steering angle imparting device can be made extremely small.

[0028]

[Effect of device]

 The electric steering angle imparting device of the present invention is constructed and operates as described above, but the diameter of the device can be reduced by reducing the distance between the electric motor and the housing. Therefore, it is possible to install in a narrow space, and it becomes easy to design a four-wheel steering device incorporating an electric steering angle imparting device.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a schematic plan view of a four-wheel steering device incorporating a conventional electric steering angle imparting device.

FIG. 5 is a perspective view of a conventional electric steering angle imparting device.

[Explanation of symbols]

 1 Steering Wheel 2 Steering Angle Sensor 3 Vehicle Speed Sensor 4 Controller 5 Electric Motor 6 Output Shaft 7 Worm 8 Worm Wheel 9 Transmission Shaft 10 Pinion 11 Output Shaft 12 Rack 13 Tie Rod 14 Knuckle Arm 15 Rear Wheel 16 Housing 17 Output Shaft 18 Rack 19 Pinion 20 Rolling bearing 21 Cylinder part 22 Pressing piece 23 Compression spring 24 Lid piece 25 Joint 26 Encoder 27 Input shaft 28 Electric motor 29 Male screw part 30 Large diameter part 31 Lid body 32 Nut piece 33 Female screw 34 Worm wheel 35 Ball bearing 36 Inner ring 37 Outer ring 38 Lock nut 39 Worm 40 Ball bearing 41 Sliding bearing 42 Joint 43 Encoder 44 Space

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A housing, an output shaft which is supported inside the housing so as to freely displace only in the axial direction, and which imparts a steering angle to the wheels in association with the displacement in the axial direction. A male screw portion fixedly provided on the outer peripheral surface of the intermediate portion, a nut piece rotatably supported inside the housing in a peripheral portion of the male screw portion, and an electric motor for rotationally driving the nut piece. The male screw portion and the female screw formed on the inner peripheral surface of the nut piece are provided with an electric steering angle irreversibly engaged so that torque can be transmitted only from the nut piece to the output shaft. Applicator.